diff --git a/coe_mirror.py b/coe_mirror.py
index 393af89..166bddb 100644
--- a/coe_mirror.py
+++ b/coe_mirror.py
@@ -168,13 +168,16 @@ def release_lock(lock_fd: int) -> None:
 
 
 def probe_target() -> bool:
-    """Probe target directory health. Write tiny file, read back, delete. Return True if healthy."""
+    """Probe target directory health. Write tiny file, read back, delete. Return True if healthy.
+
+    When MOUNT_ROOT is configured, first verify it is a live mountpoint and TARGET_DIR is under it; return False (queue to pending) otherwise.
+    """
     try:
         if MOUNT_ROOT is not None:
             if not MOUNT_ROOT.exists() or not os.path.ismount(str(MOUNT_ROOT)):
                 logger.warning("mount_root %s is not a live mountpoint; target unavailable; queuing locally", MOUNT_ROOT)
                 return False
-            if not (TARGET_DIR == MOUNT_ROOT or TARGET_DIR.is_relative_to(MOUNT_ROOT)):
+            if not TARGET_DIR.is_relative_to(MOUNT_ROOT):
                 logger.warning("target_dir %s is not under configured mount_root %s; misconfig; queuing locally", TARGET_DIR, MOUNT_ROOT)
                 return False
 
diff --git a/tests/test_coe_mirror.py b/tests/test_coe_mirror.py
index 4b74b2e..1a3f027 100644
--- a/tests/test_coe_mirror.py
+++ b/tests/test_coe_mirror.py
@@ -37,6 +37,7 @@ def mock_paths(tmp_path, monkeypatch):
     pending_dir.mkdir()
     log_dir.mkdir()
 
+    monkeypatch.setattr(coe_mirror, "MOUNT_ROOT", None)
     monkeypatch.setattr(coe_mirror, "TARGET_DIR", target_dir)
     monkeypatch.setattr(coe_mirror, "PENDING_DIR", pending_dir)
     monkeypatch.setattr(coe_mirror, "LOG_DIR", log_dir)